House of horrors

Air pollution created by cooking, heating and vacuuming could be having significant adverse effects on health. Levels of potentially dangerous particles, known as PM10s, can be much higher inside houses than outside, according to a new report from Britain's Institute for Environment and Health, part of the Medical Research Council.

High levels of PM10s - particles smaller than 10 micrometres across - have been linked to increased risks of asthma, heart attacks and reduced lung function.

PM10s are released in car exhaust fumes, for example. But they are also produced during cooking, and when gas burns in cookers or boilers. Clouds of the particles can be stirred up by vacuuming or by simply moving around the house, says Paul Harrison, the Institute's acting director.

"As soon as you get an indoor source of the particles, the levels become considerably higher than you would measure outside," says Harrison. "An individual's exposure to PM10s is very much driven by indoor exposure - so those levels could be very important."

Harrison's team has reviewed reports on the dangers of PM10s and research into sources of indoor pollution from around the world.

Studies found that when cooking was taking place at the time of PM10 monitoring, it contributed 25 per cent of the total. Other indoor sources contributed 19 per cent, and 56 per cent of the PM10s had drifted in from outdoors.

The mixture of PM10s found inside is clearly different to that found outside. "But whatever the source, the health effects are probably the same," says Harrison.

Research on PM10s has mostly concentrated on outdoor sources. But "people who are most vulnerable - the sick, elderly, or infants - are not actually walking the streets very much" Harrison points out.

The report recommends new research into ways to reduce indoor exposure to PM10s.

Increased insulation of homes over the past few decades has probably made the problem worse, Harrison thinks. But using an extractor fan while cooking and a vacuum cleaner fitted with a small particle filter would help lower levels, he says.

He thinks general awareness of the indoor risks also need to be raised. "Research into indoor sources has been bubbling away for a while, but I think it's increasingly getting the attention it deserves."

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